1. Field of the Invention
The present invention relates generally to contour measuring devices for measuring the contour of hot-strip rolls installed in a roll stand during a rolling process and, more particularly, to a contour measuring device comprised of a plurality of distance sensors that extend along the length of the hot-strip roll in a perpendicular and non-contacting manner.
2. Description of the Prior Art
A measuring device for measuring the contour of a hot-strip roll is known from JP Abstract 60-180610 A. A four-roll stand for rolling metal strips, which has two working rolls and two support rolls mounted rotatably in chucks, is known from DE-A-2 260 256. During the rolling process, heavy wear occurs on the roll surfaces, especially those of the working rolls. Local depressions, known as wear marks, form in the roll surface, particularly in the area near the edges of the material being rolled. These wear marks intensify when metal strips of the same width are rolled continually. As the rolls become more worn, the flatness of the rolled metal strips declines drastically. In order to prevent or reduce this effect, it is necessary to regrind or change the rolls at cyclical intervals. In general, these intervals are established inflexibly on the basis of operational experience. However, because the wear on the rolls occurs irregularly, the restoration cycles of the rolls or roll surfaces are not implemented in an optimal, i.e., an economical manner.
In order to determine the precise timepoint for regrinding or exchanging the rolls, it is necessary to continuously measure the wear undergone by the rolls. This can be done, for example, by measuring the contour of the roll surface at suitable chronological intervals and with suitable measurement accuracy. It is then possible to accurately determine the wear on the rolls from the difference between the original roll contour and the current roll contour. For the purpose of such measurement, a distance sensor is usually guided longitudinally across the roll surface.
A mechanical distance sensor used in roll grinding machines is known from EP-B1-0239161. However, it is not possible using this distance sensor to directly measure the contour of the hot roll surface in the stand, because of the unfavorable ambient conditions, particularly the high temperatures, in the region of the rolls. Due to thermal expansions, the measurement error is too large. Furthermore, it takes a relatively long time to carry out measurement with such a measuring device. This is a disadvantage, because after even one minute the thermal barrel of the roll begins to reform significantly, while the primary object of measurement is to obtain an accurate picture of the thermal barrel, i.e., the true contour of the hot roll surface, during the rolling process. Highly accurate determination of the roll contour during the rolling process is not possible using a measuring device of this type.